Permeability Estimation from Field Data

Abstract

Strong correlations exist between core measured permeability values and the phase velocity and attenuation of the tube wave obtained from full waveform acoustic logs. A number of authors have applied the Biot theory to the borehole wave propagation problem in order to explain the observed correlations with reasonably good success. In this paper we present two methods of estimating the absolute in-situ permeability from acoustic log data. Comparisons between measured tube wave velocity and attenuation and model predictions indicate that the Rosenbaum formulation of the Biot model can explain most of the tube wave attenuation data. Based on these findings, an inverse problem is formulated to estimate in-situ permeability from tube wave attenuation measurements using the Biot-Rosenbaum model. Resulting permeability estimates from two field data sets are in agreement with smoothed core permeability measurements. A second estimation method is based on tube wave velocity measurements. By taking the difference between the measured tube wave travel time and the calculated elastic travel time, a new measure is obtained which is referred to as the AAT value. A cross plot of logarithmic core permeability values versus AAT values for data from two different lithologies gives an excellent linear trend for the permeability range of 0.1 to 2000 millidarcies.